you should always build the battery with the cells in series first and then tie the packs together in parallel through the sense wires. it does not require a large wire for the parallel connection because the current flows in the serial direction, not parallel.

dnmun wrote:you will have to post up a picture of your battery pack. i have never seen lipo packs assembled with the cells wired in parallel.

Cannot tell you about his pack.. but all my higher power lipos are parallel then serial. My thunersky 6000mah 11.1v are 3 parallel 2000mah cell pack, then put in series to get 11.1v.
I would expect any serious mah pack is that way since its easier to solder the tabs sections then add wires to make serial than it is to add wires to parallizes packs, then add more wires to parallelize them. Here is a shot of one of them you can see the vertical stacking of cells (parallel soldered at the tabs) and the the length is the series.

20141017_214906.jpg (116.74 KiB) Viewed 3809 times

Its not too uncommon to have serial serial parallel, e.g. 4 packs of 11.1vs in series where the pack are themselves 3S of sub pack of 3p.

If you look at the RC lipo wiring site (http://scriptasylum.com/rc_speed/lipo.html) that is what they think is the normal configuration series of parallel. There are dozens of packs on hobby king that are 3s2p.

That being said I'm looking at building a 12ah 7S pack that is a serial connection of two 2 packs in parallel of 3sx3p *6ah) lipo and a 1Sx6p pack that I'm building out of cells groups pulled from other packs where one of the serial elements died. No standard name for this kind of thing and not sure exactly how I'll charge it other thank taking them out of the bike to balance. After some testing I expect I'll get a BMS and build an adapter so i can bulk charge it. I know this is a bit weird, but I'm doing this as a stop gap.. and I want to keep my thundersky for UAV flying (which is why I bought them) and my controller will not work at >30V and the sag from 6S was too much so I wanted 7s and had the cells to make it.

This thread was helpful as I did not think about parallelizing across the packs (I've only done parallel cells).. but can see that if they are already balanced and close it would work to keep them in balance and that will make it easy to do a BMS while keeping the packs usable for UAVs;-)

Hmm hopefully you have 4 3s 5000mah batteries.. neither order works with just 3 batteries..

With 4 then you can really connect in either order, you get 6 in one, half a dozen in the other -- only real issue is how you will charge them and how you balance them.

You can 2 in parallel to get a 3s2p 10000mah battery , then 2 of those in series.. but that takes 4 batteries, 2 parallel harnesses and 1 series harness. If you want you as described in this thread you can then rewire the balance connectors on them and make a single 6s connector to charge the whole thing as big 6s battery. Or you can disconnect the series connector and charge as 2 halves of 3s.

If you do series first then parallel you need 4 batteries, 2 series harness and 1 parallel.. (so less wires in the harnesses). To charge you'll need to disassemble to the individual packs.

In my view, the advantage of parallel cells first is that the cells naturally equalize and you can treat the whole pack as a single "cell" for balance/monitoring. For parallel packs you can connect the balance leads and still treat them that way.

DrInnovation wrote:Hmm hopefully you have 4 3s 5000mah batteries.. neither order works with just 3 batteries..

With 4 then you can really connect in either order, you get 6 in one, half a dozen in the other -- only real issue is how you will charge them and how you balance them.

You can 2 in parallel to get a 3s2p 10000mah battery , then 2 of those in series.. but that takes 4 batteries, 2 parallel harnesses and 1 series harness. If you want you as described in this thread you can then rewire the balance connectors on them and make a single 6s connector to charge the whole thing as big 6s battery. Or you can disconnect the series connector and charge as 2 halves of 3s.

As of now that is what I do. I run them first in parallel than in series and charge all 4 batteries in parallel.

Question is can I just charge them in series instead of taking it apart and charging It in Parallel?
If so I will put the balance leads the same way as the batteries themselves, first in parallel than in series. (So it will look like a 6s cell battery in the charger)

DrInnovation wrote:If you do series first then parallel you need 4 batteries, 2 series harness and 1 parallel.. (so less wires in the harnesses). To charge you'll need to disassemble to the individual packs.

Didn't neptronix who made this thread put his 5s batteries in series then parallel and charge them as one pack? And he did the same for the balance leads, first in series than in parallel.

DrInnovation wrote:In my view, the advantage of parallel cells first is that the cells naturally equalize and you can treat the whole pack as a single "cell" for balance/monitoring. For parallel packs you can connect the balance leads and still treat them that way.

As of now that is what I do. I run them first in parallel than in series and charge all 4 batteries in parallel.

Question is can I just charge them in series instead of taking it apart and charging It in Parallel?
If so I will put the balance leads the same way as the batteries themselves, first in parallel than in series. (So it will look like a 6s cell battery in the charger)

Yes, if you have a 6s charger and get a parallel charging board (like the pic in the first threat) or rewire them into a 6s connector you can charge them all at once without splitting the pack.
You can do that in either configuration (S-P or P-S) as long as you are careful about the ordering or the balance wiring and have a charger that supply enough currrent (or just take longer).

BShady wrote:

DrInnovation wrote:If you do series first then parallel you need 4 batteries, 2 series harness and 1 parallel.. (so less wires in the harnesses). To charge you'll need to disassemble to the individual packs.

Didn't neptronix who made this thread put his 5s batteries in series then parallel and charge them as one pack? And he did the same for the balance leads, first in series than in parallel.

Yep he did. In a later post he explained why..

neptronix wrote:

nicobie wrote:Isn't it common practice to hook up batteries in parallel then in series?

Maybe it is, but whatever is most convenient will work all the same.

If you have an icecube57-style charging setup ( big parallel packs, which get unseriesed and then paralleled in order to charge with a a high power low cell count charger ), it makes sense to think in parallel groups.

I prefer a middle ground. I make permanent 10AH 10S packs out of 4 5S bricks after testing all bricks. I can cut my usual 20AH 36v pack in half and put the other half in my lady's bike and ride along with her, or i can run the full 20AH ( and then some, as you can see ) alone, or run 20S 10AH with a series connector.

he likes that S then P design so he can break the packs apart to use it as two pack, or keep the big pack it in parallel for longer runs.
With a 4-way parallel cable (which he did not show but is trivial to make) he can combine 4 of the 10S (4x5sx2) serialized packs to get 20aH.. or can use a 2-way parallel adapter with 2x5x2 packs for just 10Ah. Though I think that if he is splitting as he described the parallel connections (4 way parallel on the balance), he also either has to split the pack into 10ah parts to charge or has to reconnect different parallel balance approach (remove 2x4-way and do an 8-way parallel balance if he wants to charge the 20ah pack).

I think I will keep my set as P-S and will charge them in series as 6s 10ah battery.
Do I have to balance the batteries? If the batteries are in balance and they stay like that do I have to balance charge them every time? I know people who have barely ever balance charged and their batteries never died on them.

2 last qu:
I want to make 2 connection ends after I connect the batteries in series. One end will be for charging and the other will be connected to the EV controller. Could I charge the batteries if the positive lead for the EV controller is still connected to the controller? (the negative side has a switch so it will be disconnected)

my charger has a power limit of 50W how do i know if i will exceed that limit? i plan on charging a 6s 10ah battery at 3amp.

I think I will keep my set as P-S and will charge them in series as 6s 10ah battery.
Do I have to balance the batteries? If the batteries are in balance and they stay like that do I have to balance charge them every time? I know people who have barely ever balance charged and their batteries never died on them.

You should absolutely balance before you build the p-S rig.. or they will balance themselves accross pack when you connect them -- and do so potential violently. I don't know how to balance across packs without balancing the packs themselves. Balancing them is also good to ensure safe charging.. I recommend you reread the whole thread as this question is answered in the first post.
If you choose to bulk charge after that, just checking balance and voltage from time to time, is your choice.. there is risk but how much depends on the quality of your packs, how in-balance they say and how hard you push them on charge/discharge. Lots of safety issues to consider -- but I would not risk not balancing before building the pack.

BShady wrote:
2 last qu:
I want to make 2 connection ends after I connect the batteries in series. One end will be for charging and the other will be connected to the EV controller. Could I charge the batteries if the positive lead for the EV controller is still connected to the controller? (the negative side has a switch so it will be disconnected)

my charger has a power limit of 50W how do i know if i will exceed that limit? i plan on charging a 6s 10ah battery at 3amp.

I cannot really answer what your controller will do.. pragmatically the switch on neg should isolate it.. but it depends on how your system deals with the lack of ground and if anything feeds back to it.

if you are setting it as 3amp at 4volts (around when it rams down) and 6s.. that is 3amp * 24volts (4*6) =72 watts.. will probably need to dial it down to 2amp..

BShady wrote:How can you figure out how long it will take to charge your batteries completely? Lipo batteries.

Best way I know how is to measure it.. Balance charging takes a variable amount of time depending on how unbalanced the cells get and the chargers output. Even for bulk charging without rebalance, the charge process for lipos ( could be Constant-current then constant voltage for faster charging or just CV) depends very much on your charger and the state of the batteries. My balance charger tracks the time to charge so I can do one then I have a good idea of the time for the next one. When I bulk charge, my meanwell RS-150-24 charger does not track time and does not have an alarm so the first times I just checked the voltage very regularly (every 10min or so) and watched every cell -- I charge pretty conservatively ( about .5C and only charge to 28.3V for 7s (4.04v average per cell). After 3 days of bulk charge cycles watching every cell, and seeing them staying within .02v of each other, I cut back to checking on saturdays as I have to disassemble the pack do check each cell.

You might be able get a lower bound by looking at the needed energy and divided by your chargers output, but that also depends on knowing the discharge curve of the batteries in their current state.. way too hard to get a good number. So measure it once while waiting patiently around the charger and checking so you know when it finishes.. then you have a measure for your charger on your batteries. If you drain them deeper on longer trips you can build an approximate table. Best to hang around, especially on the first charges on a new harness -- I either work on something else in the garage or take my laptop or some grading out with me.

I want to make a 10s lipo set-up. I already have 4s 5ah batteries can I buy 6s 5ah batteries and run them in series to make 10s 5ah and charge them as 10s 5ah as well?

Thanks

Yes, it's possible.
The only thing that you need to do if you gonna charge with a balancer charger is to join the higher balance wire of the first Lipo with the lower balance wire of the second Lipo, because when connected in series they will have the same voltage.

I'm struggling with the concept of serial first or parallel first. I just can't visualize it. Likely because I haven't yet tried to physically lay it out. I've been hearing it fro dnmum since asking my first battery layout question. I apologize for being so thick, but regardless, I can't see it. Are there pictures or schematics showing the difference.

Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.